1. Field of the Art
The present invention relates to a laser oscillator employing a laser rod made of an yttrium aluminate crystal doped with neodymium ions, as active ions (Nd: YAlO.sub.3), and to a process for manufacturing the same.
2. Description of the Prior Art
A single Nd: YAlO.sub.3 crystal for laser use belongs to the orthorhombic system which can provide a linearly polarized laser output, without making use of a polarizer element. In addition, as compared to a crystal of yttrium aluminum garnet containing neodymium ions as active ions (Nd: Y.sub.3 Al.sub.5 O.sub.12), neodymium ions are easily doped into the YAlO.sub.3 single crystal. Hence, a laser rod containing a high concentration of active ions can be obtained.
However, a yttrium aluminate single crystal is liable to be adversely affected by ultra-violet rays and visible rays having wavelengths of 5000 A or less. For instance, if a xenon flash lamp is used as a pumping light source, the laser oscillation efficiency is greatly reduced by the pumping light having wavelengths of 5000 A or less (hereinafter this light is called "short wavelength light") among the light emitted from the xenon flash lamp. Therefore, in the prior art, measures where taken to provide a filter for cutting out the short wavelength light. The filter was inserted between a laser rod and a pumping light source lamp enclosed within a pumping cavity.
A solid state laser oscillator employing such a filter is disclosed in U.S. Pat. No. 4,039,970. This laser oscillator is constructed in such manner that the interior of the pumping cavity is partitioned into two space regions by means of a colored glass filter, which cuts out the short wavelength light. A laser rod and a pumping light source lamp are disposed in parallel to each other in their respective space regions. At the opposite ends of the laser rod there are reflecting mirrors which form a light resonator. Such a laser oscillator employing a filter has a disadvantage. The structure within the pumping cavity becomes to complex for inserting a colored glass filter. Also the light condensing efficiency for the pumping light is reduced by the surface reflection of the colored glass filter.